Herbal Remedies for Hair Loss: A Review of Efficacy and Safety

Abstract

Background

Hair loss (HL) is a prevalent condition worldwide; it can affect both males and females of different age groups. Despite the availability of many conventional treatment options, these might be linked to causing different side effects, leading to a growing interest in natural and herbal remedies (HRs). This review aims to investigate the efficacy and safety of various HRs for HL and examine the current scientific evidence behind them.

Summary

A literature search used several studies to identify relevant studies published up to March 2024. The search terms included HL, alopecia, HRs, and names of specific herbs such as rosemary, saw palmetto, onion juice, Korean red ginseng, pumpkin seed oil, azelaic acid, olive oil, coconut oil, henna, honey, rice bran extract, Ashwagandha, and amla. Studies have suggested potential benefits in promoting hair growth and treating various forms of HL. These remedies were found to be effective in different conditions, including androgenetic alopecia, telogen effluvium, and alopecia areata, through various mechanisms of action, including 5α-reductase inhibition, increased microcapillary blood flow, antioxidant effects, and modulation of the hair growth signaling pathways.

Key Messages

Natural and HRs show promise in treating HL. However, many of these studies have limitations such as lack of long-term follow-up, small sample sizes, and short treatment durations. Due to this variation in the quality of evidence, further well-designed randomized trials with larger sample sizes are required to confirm the efficacy of these HRs.

Introduction

Hair loss (HL) is an evident condition that affects both males and females of different age groups, both individual’s self-esteem and quality of life can be significantly impacted by this common issue [1, 2]. Minoxidil and finasteride are some examples of conventional treatments for HL. Although those treatments are widely available, they have been linked to different side effects such as scalp irritation, sexual dysfunction, and increased risk of prostate cancer [3, 4], leading to the growing interest in natural and herbal remedies (HRs) for HL.

HRs have been used and trusted for centuries for promoting hair growth and preventing HL [5]. Although their safety and efficacy have not been well established [6], these remedies are believed to have fewer SE than conventional drugs [7].

The potential of HRs for the treatment of HL has been discussed in different studies, and Prager et al. [7] reported that the combination of herbal extracts, such as saw palmetto (SP) and beta-sitosterol, drastically improve hair density and quality in men with androgenetic alopecia (AGA) [8]. Another study by Esfandiari and Kelly found that topical application of green tea extracts improved hair density and thickness in women with pattern HL [6]. Furthermore, studies on pumpkin seed oil (PSO) prove its blocking action of 5-alpha reductase, an enzyme that converts testosterone to dihydrotestosterone (DHT), which is implicated in HL [8, 9]. In addition, a study by Cho et al. [10] showed that administration of PSO for 24 weeks increased hair count compared to placebo administration.

Despite those findings, more research is needed to completely understand the effects of HRs on HL. This review article aimed to review the current scientific evidence in this regard and provide an evidence-based perspective on the use of HRs for HL, encouraging healthcare practitioners and patients to make informed decisions about managing this common and distressing condition.

Methodology

A comprehensive literature search was conducted using several research engines to identify relevant studies published up to March 2024. The search strategy included the following key terms: “hair loss,” “alopecia,” “herbal remedies,” “rosemary,” “saw palmetto,” “onion juice,” “Korean red ginseng,” “pumpkin seed oil,” “azelaic acid,” “olive oil,” “coconut oil,” “henna,” “honey,” “rice bran extract,” “Ashwagandha,” and “Amla.” The search was limited to articles published in the English language.

The inclusion criteria included randomized controlled trials, clinical trials, case studies, or in vitro studies investigating HRs for HL. In addition, studies involving human participants or animal models, studies reporting outcomes related to hair growth, density, thickness, and quality, and studies on potential mechanisms of action (MOA) of HRs. Also, we will focus on the most active constituent in every herb that can improve or induce hair growth. The exclusion criteria excluded studies without full-text availability, studies focusing on HL due to chemotherapy or other medical conditions, and studies investigating the efficacy of non-herbal treatments for HL.

Independent reviewers screened the titles and abstracts of retrieved articles for relevance. Full-text articles were assessed for eligibility based on inclusion and exclusion criteria. Narrative synthesis of the extracted data was performed, with focus on efficacy and safety of various HRs for HL. The potential MOA of HRs are also discussed based on available evidence.

Review of HRs for HL

Rosemary

Rosemary (Rosmarinus officinalis L.) is a well-known herb that has been extensively studied for its various applications in food and medicinal industries [11]. Recent studies have investigated the potential of rosemary oil (RO) as a natural treatment for AGA, a common form of HL affecting both genders.

A study led by Panahi et al. compared the effectiveness of daily application of RO lotion (3.7 mg/mL) to that of 2% minoxidil, a commonly used hair growth product [12]. The study involved 100 participants with AGA who were treated with either RO or minoxidil for 6 months. The results revealed that RO was as effective as minoxidil in promoting hair growth, with both treatments showing significant increases in hair count after 6 months [12]. Notably, participants in the RO group experienced results, suggesting a more favorable side effect profile for RO [12].

The hair growth-promoting properties of RO are believed to be related to its ability to enhance microcapillary blood flow, as demonstrated by Panahi et al. [13]. This increased blood circulation in the scalp may stimulate hair follicles, leading to improved hair growth. Additionally, RO has been shown to possess anti-inflammatory properties (AIP) and antioxidant properties, which may contribute to its overall effectiveness in treating AGA [11].

In addition, Murata et al. [14] found that topical application of rosemary leaf extract improved hair regrowth in mice with testosterone-induced HL. Rosemary leaf extracts were found to promote hair growth in mice when applied topically at a dose of 2 mg per day; moreover, an increase in the expression of insulin-like growth factor-1 and vascular endothelial growth factor were noted after application, both of which are important factors in hair growth.

The researchers further demonstrated that the hair regrowth was attributed to the inhibition of 5α-reductase, which was triggered by 12-methoxyrososic acid. Additionally, they noted that 12-methoxycarnosic acid, along with rosemary extract, can prevent DHT from binding to androgen receptors in the hair follicles [14]. In this study, C57BL/6 mice with testosterone-induced alopecia were treated topically with hydroalcoholic extracts of rosemary (2 mg/day/animal) and showed a significant increase in hair growth after the 16th day of treatment compared with those in the control. A hydroalcoholic extract was tested in vitro for the evaluation of 5αR enzyme activity and showed strong inhibition of the binding of DHT to its receptor. An in vitro assay in human prostate LNCaP cells indicated that 12-methoxy-sarcosalic acid had a key role in the inhibition of the 5αR enzyme and DHT/receptor binding [14].

The study has several limitations that should be noted. First, it was conducted on mice, which limits the direct applicability of the results to humans. Additionally, the study was relatively short-term, with a duration of only 5 weeks. Longer term studies would be needed to assess the sustainability of the hair growth effects and to evaluate any potential long-term side effects. Another limitation is that the exact mechanism by which hair growth was promoted is not fully understood. More research is required to explore other possible molecular pathways involved in the process [14].

These findings highlight the potential of RO as a natural alternative for managing AGA. With its comparable effectiveness to minoxidil, lower incidence of side effects, and diverse MOA, RO emerges as an attractive option for individuals seeking a more natural approach to combating HL. However, further research is necessary to confirm these results, establish optimal dosages, and determine the most effective application methods for RO in AGA treatment.

Saw Palmetto

SP, scientifically known as Serenoa repens, is a small palm tree native to the southeastern USA and has been traditionally used in herbal medicine. SP has gained recognition for its potential therapeutic properties, particularly in addressing conditions like benign prostatic hyperplasia and HL [15]. Recent studies have investigated the potential of SP extract for the treatment of AGA and telogen effluvium (TE). A comprehensive review conducted by Evron et al. [16] explored the impact of SP on AGA and TE, revealing promising results. The study suggested that SP could enhance hair count, density, and quality, particularly in cases of AGA. This attributed antiandrogenic properties of SP are believed to play a key role in promoting hair growth, by inhibiting the activity of 5α-reductase, which may help reduce the miniaturization of stimulate hair follicles caused by DHT [16].

According to this review, positive results from the use of topical and oral supplements containing SP were noted at doses ranging from 100 to 320 mg in patients with AGA and TE. Studies included in the review reported a 60% improvement in overall hair quality, a 27% increase in total hair count, increased hair density in 83.3% of patients, and stabilization of disease progression in 52% of cases. SP was well tolerated and not linked to any serious adverse events in patients with alopecia [17].

The largest randomized clinical trial to date compared the effects of daily 320-mg SP-containing tablets and 1-mg finasteride in 100 men with AGA over a 2-year period. Hair density was measured using standardized global photography, and treatment effectiveness was assessed using a 7-point clinical score scale by three expert dermatologists specializing in alopecia. The results showed that 68% of patients treated with finasteride had improved hair density scores from baseline, compared to 38% in the SP group (p < 0.05), suggesting that SP is less effective than finasteride. However, while neither treatment was clinically effective for 10% of patients, SP managed to stabilize AGA progression in 52% of cases [18].

Another study by Prager et al. showed some promise, particularly in slowing down HL and increasing hair density, even though it does not perform as well as finasteride, one limitation of this study was small sample size, as it involved only 26 participants, which makes it difficult to draw strong, generalizable conclusions. In another study by Rossi et al., only 38% of participants who used SP experienced a noticeable increase in hair density, compared to 68% of those using finasteride. In addition to its potential benefits for AGA, this review assessed SP’s impact on TE through 2 case studies, one randomized trial, and one prospective cohort study. The results indicate that SP may have potential benefits for TE, although the evidence is limited compared to its effects on AGA [16].

In terms of safety, SP is generally well tolerated, with only minor gastrointestinal including nausea, constipation, and diarrhea SE reported in some studies [12, 19–21]. SP, likely due to its hormonal effects, has been reported to cause vasomotor symptoms in premenopausal females and has been suspected of triggering early menarche in young girls. Miroddi et al. [22] documented a case of an 11-year-old girl who developed hot flashes after 2 months of treating TE with a food supplement containing SP. The hot flashes resolved after discontinuing the supplement, but 45 days later, she experienced menarche. Similarly, Morabito et al. [22] reported vasomotor symptoms in a 10-year-old girl after 3 months of using a food supplement with 320 mg of SP extract to treat hirsutism. As with the previous case, the symptoms ceased once the supplement was discontinued, and the girl experienced menarche soon afterward. Topical SP-containing agents have also been linked to minor adverse effects such as a cold sensation, mild burning, an unpleasant smell, itchy scalp, forehead acne, and allergic contact dermatitis [23, 24].

This favorable safety profile makes SP an attractive option for individuals seeking a natural alternative to conventional HL treatments such as finasteride, which can have more severe SE [25]. It is important to note that while SP has demonstrated some effectiveness in managing AGA progression and enhancing TE treatment outcomes, it may not be as potent as finasteride. However, the natural origin and favorable safety profile of SP makes it a worthwhile consideration for those who prefer a more natural approach to HL management.

Onion Juice

Alopecia areata (AA) is an autoimmune disorder that results in patchy HL on the scalp and other areas of the body. While there are various treatment options available, the use of natural remedies like onion juice has garnered attention in recent times. Onion (Allium cepa) has a long history of being used for its medicinal properties, and a recent clinical study has explored its potential in treating AA [26].

The most active constituent in onion juice believed to promote hair growth is sulfur. Sulfur is an essential component in the formation of keratin, a protein that is crucial for hair structure and strength. Onion juice is also rich in antioxidants, such as flavonoids like quercetin, which may help reduce inflammation and oxidative stress on the scalp, thereby promoting healthier hair growth [27].

The exact mechanism through which onion juice stimulates hair regrowth in AA is not yet fully understood. However, it is believed that the sulfur and phenolic compounds found in onion juice may trigger irritant contact dermatitis, potentially leading to hair regrowth by initiating antigenic competition [28].

A clinical study conducted by Sharquie and Al-Obaidi [26] involved 62 participants to assess the therapeutic efficacy of topical raw onion juice in managing AA. The treatment group, comprising 45 individuals, applied crude onion juice to their scalp, while the control group of 17 participants used plain water. Over an 8-week period, the extent of hair regrowth was evaluated. Encouragingly, the results showed that 87% of participants in the onion juice group achieved complete hair restoration, compared to only 13% in the placebo group. These findings suggest that topical application of raw onion juice could be a viable treatment option for AA [26].

The main side effect reported in this study was the unpleasant odor associated with onion juice treatment. This drawback may limit acceptability and adherence to treatment, especially in social settings [26]. Although the results of this study are encouraging, it is important to note that the sample size was relatively small, and further research with larger cohorts is necessary to confirm the effect of onion juice on treatment of AA. Additionally, the optimal concentration, frequency, and duration of onion juice application for AA management remains to be determined.

The potential mechanism of action of onion juice in promoting hair regrowth in AA is believed to be linked to its high sulfur and phenolic compound content. Sulfur’s antimicrobial properties and anti-inflammatory potential may play a role in its positive effects on hair growth. Additionally, phenolic compounds like quercetin and flavonoids, which possess antioxidant properties, could help reduce the autoimmune response associated with AA [29]. While onion juice shows a promise as a natural remedy for HL in individuals with AA, further research is needed to fully understand its effectiveness and optimal usage for hair regrowth.

Korean Red Ginseng

Korean red ginseng (KRG) is a traditional medicinal herb with a long history of use in East Asian cultures. It is renowned for its diverse pharmacological properties, which encompass antioxidant, anticancer, antistress, and anti-diabetes effects [30]. A recent study sought to assess the efficacy and safety of KRG in treating AA by comparing two cohorts of patients: one group receiving corticosteroid intralesional injections (ILI) alone and another group receiving ILI in conjunction with KRG supplementation over a 12-week period. The objective was to explore any synergistic benefits that KRG might offer in conjunction with conventional AA therapies. The outcomes revealed that both groups exhibited enhancements in hair density and thickness [31]. However, there were no statistically significant differences between the two groups in terms of these objective measures. This suggests that the addition of KRG to ILI treatment does not provide a significant quantitative benefit over ILI alone [31].

In this study, standardized global photographs of the leading site of the bald scalp were obtained at baseline (0 week) and 12 weeks and then assessed and reviewed in a blinded manner by an expert panel of three dermatologists at the end of the trial. Interestingly, the expert panel’s assessment of global photographs showed a significantly better improvement in the group treated with KRG and ILI than in the group receiving ILI alone (p = 0.047) [31]. This finding suggests that KRG may have a potential qualitative benefit in AA treatment by enhancing the overall appearance of hair regrowth. The mechanism underlying KRG’s potential effects on AA is not fully understood [31]. However, it is speculated that various bioactive compounds present in KRG, such as ginsenosides, may play a role in modulating the immune response and reducing inflammation [32]. AA is an autoimmune disorder characterized by an inflammatory response targeting the stimulate hair follicles, and the anti-inflammatory potential of KRG may help alleviate this response.

Additionally, KRG’s documented antioxidant characteristics may serve to shield hair follicles from oxidative stress, which is a factor implicated in the development of AA [33]. Mitigating oxidative damage could potentially contribute to the overall enhancement in hair regrowth [33]. While the findings of this study suggest a promising role for KRG in AA treatment, it is crucial to acknowledge the study’s limitation in terms of sample size. Further investigations involving larger cohorts are imperative to validate these initial insights. Additionally, the optimal dosage and duration of KRG supplementation for AA management remains to be determined.

The active compounds in KRG, called ginsenosides, are believed to improve hair health by increasing scalp circulation, enhancing nutrient delivery to hair follicles, and reducing inflammation and oxidative stress. Ginsenosides also promote hair growth by regulating the hair growth cycle, particularly by extending the anagen (growth) phase. Multiple studies have supported the efficacy of KRG in treating HL. For example, research by Shin et al. (2016) found that KRG extract improved hair density and thickness in patients with AGA. The study suggested that the positive effects on hair growth were due to KRG’s ability to inhibit 5α-reductase, the enzyme responsible for converting testosterone to DHT, a key factor in HL [34].

Pumpkin Seed Oil

Pumpkin (Cucurbita pepo), a North American squash, is the source of PSO, which has been found to contain high levels of phytosterols [35]. Phytosterols are plant-derived compounds that have been shown to possess antioxidant, and antiandrogenic properties [36, 37]. In AGA, phytosterols are believed to inhibit the activity of 5α-reductase. To evaluate the effectiveness of PSO in treating AGA, Cho et al. [10] conducted a randomized study involving 76 men with mild-to-moderate AGA. Participants were administered either 400 mg PSO or placebo daily for 24 weeks. This study assessed changes in hair count and patient satisfaction as primary outcomes.

The study’s findings showed that core of self-assessment improvement and that of satisfaction were higher in the PSO-treated group than in the placebo group (p = 0.013 and 0.003, respectively). Additionally, the PSO-treated group expressed more hair growth after therapy than at baseline as opposed to the placebo group (p < 0.001). Furthermore, in PSO-treated men, the mean hair count increased by 40% compared to only 10% in placebo-treated group (p < 0.001). The two compared groups did not differ significantly in terms of adverse effects. These findings suggested that the participants found the treatment to be well tolerated and effective [19]. Although these results imply that PSO might be a viable natural remedy for AGA, it is crucial to recognize certain research limitations. Additional components like gamma-linolenic acid and other nutrients were included in the PSO supplement used in this study, which might have contributed to the results that were seen, so a further extensive investigation is necessary to identify the precise impacts of PSO on hair growth promotion.

Furthermore, the study focused largely on vertex HL, and no information was provided about the effects of PSO on frontal alopecia. Hence, it is crucial to assess the effectiveness of PSO in treating HL in different scalp areas since AGA can present itself in a variety of ways in distinct scalp regions [19]. PSO’s high phytosterol content, especially beta-sitosterol, is likely to be the mechanism underpinning its ability to promote heart disease [38]. Because beta-sitosterol limits 5α-reductase activity, less testosterone is converted to DHT [15]. PSO may aid in promoting hair growth and preventing the shrinkage of stimulate hair follicles by adjusting the hormonal environment in the scalp [15].

In conclusion, pumpkin (C. pepo) contains several active constituents that contribute to its effectiveness in promoting hair growth. The most notable of these are phytosterols, particularly β-sitosterol, which is known to inhibit 5α-reductase, an enzyme responsible for converting testosterone to DHT, a key factor in AGA. Additionally, the oil extracted from pumpkin seeds is rich in essential fatty acids, vitamins, and antioxidants, which nourish the scalp and improve hair health. Studies have shown that these compounds can enhance hair density and strength [34, 38].

Azelaic Acid

Azelaic acid is a naturally occurring dicarboxylic acid, which has gained attention as a potential treatment for female pattern hair loss (FPHL). This substance is created by the fungal mycelia Pityrosporum during its metabolic activities, and it is also present in rye, wheat, barley, and among other crops [39, 40]. Recent research has investigated the processes that might be responsible for the possible effects of azelaic acid on HG. Moreover, azelaic acid is a strong inhibitor of 5α-reductase; Stamatiadis et al. showed that the inhibition of 5α-reductase may help avoid HL and promote hair growth [41].

Apart from azelaic acid’s inhibitory effect on 5α-reductase, azelaic acid also controls the expression of Gli1 and Gli2 proteins, which are crucial for the regulation of hair growth [42]. Additionally, Mastrofrancesco et al. discovered that azelaic acid shields hair bulge cells from ultraviolet B damage, indicating that it might aid in maintaining the integrity of hair follicles [43].

In one research with 26 women, two groups were randomly assigned to receive topical solutions containing either 5% azelaic acid or 2% minoxidil twice a day to assess the clinical efficacy of azelaic acid in treating FPHL. This study used minoxidil, a commonly used medication for HL, as a point of comparison [44]. The study’s findings demonstrated that at 2, 4, and 6 months of treatment, both 2% minoxidil and 5% azelaic acid significantly increased hair density and diameter. Given the similar results of the two therapies, azelaic acid could prove to be a useful substitute for minoxidil in the treatment of FPHL [44]. Azelaic acid has a better safety record and might be used as a substitute of minoxidil in certain patient populations, for example, during pregnancy and nursing. However, no significant differences were observed between compared groups regarding hair density and hair shaft diameter [44].

Olive Oil

Since ancient times, olive oil which is made from the fruit of the olive tree (Olea europaea) has been utilized for a variety of purposes in cooking, cosmetics, and medicine. Since it is an essential oil, olive oil has drawn interest for its possible advantages in fostering healthy hair and treating a range of hair-related issues [45]. When used in hair care products, olive oil has been shown to offer nourishing and moisturizing qualities in addition to its possible effects on hair growth [46]. To increase the softness, gloss, and manageability of hair, a few drops of olive oil can be put straight to the wash or used in the last hair rinse. Moreover, olive oil has long been used to treat a variety of scalp issues, including dandruff and inflammation [47]. Olive oil’s favorable effects on scalp health may be attributed to its antibacterial and anti-inflammatory potential characteristics.

Rich in antioxidants, vitamin E, and fatty acids, olive oil helps moisturize the scalp, strengthens hair follicles, and promotes healthy hair growth. Its AIP may also help reduce scalp irritation [39]. Olive oil is rich in fatty acids, primarily oleic acid, which penetrates the hair shaft, providing deep moisture and preventing dryness. This helps reduce frizz and adds softness and shine to the hair [39]. The vitamin E and antioxidants in olive oil protect hair from environmental damage and free radicals, strengthening the hair strands and reducing breakage and split ends [40]. Olive oil has anti-inflammatory and antibacterial properties, which can help soothe an irritated scalp and reduce dandruff. Massaging olive oil into the scalp enhances blood circulation, promoting a healthy scalp and encouraging hair growth [41]. Olive oil’s ability to nourish hair and reduce oxidative stress on the scalp makes it effective in reducing HL. Its emollient properties help strengthen hair follicles, supporting thicker and healthier hair.

While traditional methods and anecdotal evidence have primarily supported the use of olive oil in hair treatment, more systematic research has recently been conducted by scientists. There is a wealth of research on the advantages of olive oil for the skin, but less is known about how it affects hair [48].

Although olive oil is often touted for its various health benefits, there is limited scientific research specifically exploring its effectiveness in treating HL. While it is rich in antioxidants and healthy fats that may contribute to scalp health and hair nourishment, the evidence supporting its direct impact on hair growth remains largely anecdotal. Given the popularity of olive oil in traditional hair care, it is essential to conduct more rigorous studies to determine its true efficacy.

Further research should focus on understanding the mechanisms by which olive oil could influence hair growth, whether through improving scalp health, reducing inflammation, or enhancing hair follicle function. Larger clinical trials and long-term studies are needed to provide clear evidence on its effectiveness, optimal application methods, and potential side effects. Without such studies, the role of olive oil in combating HL remains uncertain, and its use as a proven treatment remains speculative.

Coconut Oil

Because of its distinct composition and possible health advantages, coconut oil, which is extracted from the fruit of the coconut tree (Cocos nucifera), has grown in favor as a natural hair care product, due to its great affinity for hair protein which is one of its most remarkable qualities. Lauric acid is the main fatty acid component of coconut oil, making up almost half of its total fatty acid concentration [49]. It is a medium-chain fatty acid with a straight linear chain and a low molecular weight. Its chemical structure is thought to be responsible for this great affinity and attraction [50]. Compared to other oils with bigger and more intricate molecular structures, coconut oil can enter hair shafts more readily because of these properties.

Rele and Mohile investigated the effects of mineral, sunflower, and coconut oils on the prevention of hair damage, Coconut oil has lauric acid, which penetrates the hair shaft, reducing protein loss and protecting hair from damage. It is also known for its antimicrobial and antifungal properties, keeping the scalp healthy [42]. When these oils were used as prewash and post-wash grooming solutions on both damaged and undamaged hair, the researchers assessed the amount of protein lost. According to the data, the only oil that considerably decreased protein loss in both damaged and undamaged hair was coconut oil [51]. The nature and structure of coconut oil are thought to be responsible for its capacity to permeate hair shafts and minimize protein loss. Coconut oil’s lauric acid can enter the hair’s cortex and cuticle, where it binds to proteins in the hair, especially keratin filaments [51]. This binding helps prevent hygral fatigue, a process that happens when the hair is frequently exposed to water and experiences swelling and shrinking and can weaken and damage the hair [46].

Coconut oil has been shown to have additional positive benefits on hair health in addition to its ability to protect proteins. According to another study by Rele and Mohile, using coconut oil on the hair enhanced its manageability, reduced frizz, and increased gloss [52]. The lubricating effect of coconut oil on the surface of the hair, according to the authors, may be a factor in these advantages [52]. In addition, coconut oil has long been utilized as a home cure for dandruff and other irritations of the scalp [45]. The potential benefits of coconut oil for scalp health may be attributed to its antibacterial activity and the antioxidant properties of lauric acid and other fatty acids [53].

In conclusion, coconut oil is an excellent moisturizer due to its high content of medium-chain fatty acids, especially lauric acid [43]. It penetrates the hair shaft, providing deep hydration and preventing dryness and frizz, making hair softer and more manageable. Coconut oil helps reduce protein loss in both damaged and undamaged hair. It forms a protective barrier around the hair, preventing damage from environmental factors, heat styling, and chemical treatments, thus maintaining hair strength [39, 44]. Moreover, coconut oil has antimicrobial properties that help fight scalp infections and dandruff [54].

Lawsonia inermis (Henna)

Lawsonia inermis L., also known as Lawsonia alba or henna, is a plant species belonging to the Lythraceae family. It is the only species within the genus Lawsonia that has been widely used for centuries as a natural dye for hair, skin, and nails [45, 46]. Henna is a natural dye that strengthens hair, improves hair texture, and helps prevent dandruff. It also has antifungal properties that keep the scalp clean [47].

Recent research has examined how Lawsonia inermis affects various hair phenotypes, with an emphasis on the plant’s possible advantages for hair morphology and health. Dweck’s investigation looked at the morphological alterations in hair fibers following henna treatment. The findings demonstrated that henna treatment reduced cuticle lifting, giving the hair a smoother, healthier appearance [55]. There have also been reports of henna’s preventive effects on the structure of hair shafts [46]. All hair phenotypes showed an increase in diameter with henna application, indicating that it might aid in the strengthening and thickening of hair fibers [56].

Henna has been used traditionally as a natural cure for a variety of hair and scalp issues. In addition to its benefits for morphology, henna may be used to treat dandruff, irritation of the scalp, and HL, according to a review by Semwal et al. [57]. Henna’s positive effects on scalp health may be attributed to its antibacterial action [48] and anti-inflammatory potential [58]. The treatment effects of henna and other herbs for AGA in mice were examined in a study by Zheng et al. after administering testosterone to mice to cause HL, they received top-down herbal therapy for 35 days [59]. All the plants encouraged new hair growth, but henna had the biggest impact, changing the color of the skin and increasing hair density. In comparison to controls, henna also decreased the amounts of testosterone and DHT in the skin. These findings imply that henna and other herbs might be useful in treating AGA [59]. However, no significant variation was observed between plants in both of serum testosterone and DHT levels or level of 5α-reductase type Ⅱ in the skin. Furthermore, it has been noted that applying henna to hair enhanced its general appearance and manageability by decreasing frizz and enhancing shine [46]. Henna has also been shown to offer nourishing and moisturizing qualities when used as a hair treatment.

Honey

Honey is produced by bees from the nectar of the flowers. It is a supersaturated solution composed primarily of fructose and glucose, along with a complex mixture of proteins, amino acids, vitamins, minerals, and other components [49]. Honey has been used for centuries in traditional medicine for its potential health benefits, including its application in wound healing and skin care [50]. Recent studies have investigated the potential benefits of honey on scalp health, particularly in context of treating scalp conditions such as folliculitis decalvans. In a case study by Alangari et al. [51], a patient with folliculitis decalvans presented with painful and swollen scalp pustules, as an alternative treatment, the patient was advised to use manuka honey, a specific type of honey derived from the nectar of the manuka tree (Leptospermum scoparium) native to New Zealand. Manuka honey has been reported to have potent antimicrobial and anti-inflammatory potential, which may contribute to its potential benefits for skin and scalp health [52]. The vitamins and minerals in honey, particularly B vitamins, promote healthy hair growth. Honey stimulates the hair follicles, encouraging new hair growth and improving hair density [53]. After applying manuka honey to the affected areas of the scalp, the patient experienced significant improvement in symptoms. The painful and swollen pustules resolved completely, and the patient reported reduced scalp discomfort [52]. In addition, another case report by Yeh et al. showed very good results and prolongation of the remission period with manuka honey combined with cephalexin in a 20-year-old patient with biopsy proven folliculitis decalvans [60].

The potential health benefits of honey for scalp have been attributed to its unique composition and properties. Honey contains various bioactive compounds such as flavonoids and enzymes, which have been reported to have antioxidant, antimicrobial, and anti-inflammatory potential [55]. Honey has been used as a natural ingredient in hair care products because of its moisturizing and conditioning properties, as it may help reduce scalp inflammation, combat bacterial and fungal infections, and promote wound healing. Furthermore, Burlando and Cornara reviewed the use of honey in skin and hair care products, highlighting its potential to improve hair softness, shine, and manageability. The potential side effects of using honey in hair care include allergic reactions, such as itching or redness, particularly for those sensitive to bee products. Its sticky texture can make it difficult to rinse out, leading to product buildup. Excessive use may also result in overly oily or weighed-down hair, especially for those with fine or oily hair. Additionally, honey may increase sensitivity to sunlight for some individuals [50].

Rice Bran Extract

Rice (Oryza sativa) is a staple food for a significant portion of the world’s population, with an annual production of approximately 600 million tons worldwide [56]. Most rice production occurs in Asia, accounting for approximately 95% of total output [57]. During the rice milling process, rice bran is generated as a major byproduct, representing 8% of the milled rice [58].

Rich in inositol, rice bran extract nourishes hair and helps prevent premature graying [59]. It also contains antioxidants and vitamin E that support scalp health and enhance hair strength [61, 62]. The extract contains essential fatty acids, including omega-3 and omega-6, which provide deep nourishment to the scalp and hair, helping to maintain moisture and preventing dryness and frizz [63]. Rice bran extract is rich in antioxidants, such as vitamin E and ferulic acid, which help neutralize-free radicals that can cause premature graying of hair. By protecting the hair from oxidative stress, it helps maintain natural hair color [64]. The AIP of rice bran extract help soothe an irritated or itchy scalp. It also reduces dandruff and keeps the scalp healthy, creating an ideal environment for hair growth [63]. The high content of vitamin E and antioxidants in rice bran extract helps repair damaged hair and restore natural shine, giving hair a healthy, lustrous appearance [65].

Rice bran has traditionally been used for various purposes, with 20–30% being utilized for oil production, and the remaining portion discarded or used as livestock feed and fertilizers [58]. However, recent studies have shed light on the numerous health benefits associated with rice bran extract, including antioxidant [58], anticancer [66], and antihyperlipidemic activities [67]. In addition to these health benefits, rice bran extract has been reported to exhibit 5-α-reductase inhibitory activity in vitro [68], and by inhibiting this enzyme, rice bran extract may prevent or alleviate HL [69].

To investigate the hair growth-promoting effects of rice bran extract in vivo, a study conducted by Choi et al. [70] compared the efficacy of rice bran extract to that of 3% minoxidil, a widely used topical treatment for HL. The study involved the topical application of rice bran extract to the dorsal skin of mice, and the results were assessed using various parameters including hair growth, hair length, and histological analysis of stimulate hair follicles [70]. The findings of this study revealed that rice bran extract exhibited hair growth-promoting potential comparable to that of 3% minoxidil [70]. Treatment with rice bran extract resulted in a significant increase in the number of stimulated hair follicles compared with that in the control group. Additionally, the rice bran extract-treated group showed a higher percentage of stimulated hair follicles in the anagen phase (active growth phase) and a lower percentage in the telogen phase (resting phase) than the control group [70]. The mechanisms underlying the hair growth-promoting effects of rice bran extracts are not yet fully understood [71].

Ashwagandha (Withania somnifera)

Ashwagandha, known as Withania somnifera or Indian ginseng, is an ancient medicinal herb that has been extensively used in various formulations owing to its numerous health benefits [72]. Pharmacological investigations have revealed that Ashwagandha possesses a wide range of properties, including antioxidants, anti-inflammatory, memory-enhancing, sleep-inducing, and anxiolytic activities [73]. One of the most notable effects of Ashwagandha is its adaptogenic property, which has been used for centuries to reduce stress [73]. Ashwagandha helps lower cortisol, the stress hormone, which can disrupt hair growth and lead to hair thinning. By managing stress, it supports a healthier hair growth cycle [74]. Stress plays a significant role in HL, and the stress-reducing effects of Ashwagandha may contribute to its potential as a natural remedy for HL [75]. Moreover, Ashwagandha stimulates DHEA (dehydroepiandrosterone) production, which helps strengthen hair and prevent breakage.

A study conducted in India evaluated the hair growth potential of an aloe vera gel-based herbal formulation containing W. somnifera (Ashwagandha) fruit extract [76]. The study was performed on male Wistar rats, and the results showed that hair growth initiation occurred earlier in the group treated with the Ashwagandha formulation than in the control group that received only aloe vera gel. In the control group, hair growth initiation was observed on the 11th day of the study, whereas in the Ashwagandha group, it occurred on the 10th day. The study presents several limitations that should be considered. First, the treatment duration was relatively short, lasting only 30 days, which may not provide insights into the long-term effectiveness and safety of the extracts. Moreover, since the research was conducted on an animal model, the results may not directly translate to human applications, underscoring the need for further studies and clinical trials to validate the effectiveness of W. somnifera (Ashwagandha) in promoting hair growth.

The mechanisms underlying the potential hair growth-promoting effects of Ashwagandha are not fully understood. However, it is speculated that the antioxidant and anti-inflammatory activities of Ashwagandha may play a role in its beneficial effects on hair health [74]. Oxidative stress and inflammation have been implicated in the pathogenesis of HL, and the presence of bioactive compounds, such as withanolides in Ashwagandha, may help combat these factors [77, 78].

Amla (Phyllanthus emblica L.)

Amla, also known as Phyllanthus emblica L., is a traditional HR that has been used for centuries to prevent and treat various ailments, including HL [79]. The fruit of the amla plant is widely recognized for its nutritional and medicinal properties, making it a popular ingredient in many herbal formulations [80]. P. emblica L. is rich in a wide range of phytochemical compounds, including tannins, mosaic acids, amino acids, alkaloids, flavonoid glycosides, phenolic glycosides, and terpenoids [81]. These bioactive compounds are believed to contribute to the therapeutic effects of amla, including its potential benefits to hair health [82].

The mechanisms underlying the HG-promoting effects of amla are not fully understood; however, several theories have been proposed. One possible mechanism is the antioxidant activity of amla, which may help protect and stimulate hair follicles from oxidative stress and damage [83]. Oxidative stress has been implicated in the pathogenesis of HL, and the presence of antioxidant compounds, such as tannins and flavonoids, in amla may help combat this process [84].

The antioxidants in amla protect hair follicles from damage caused by free radicals, helping prevent HL and premature graying. Amla also has AIP that support a healthy scalp [85]. Inflammation is associated with HL, and the anti-inflammatory compounds present in amla may help reduce inflammation in the scalp and promote hair growth [86]. Although recent trials have provided promising evidence for efficacy of amla syrup in treating female AGA, further research is needed to fully understand its MOA and to determine optimal dosage and duration of treatment [71].

Conclusion

HRs have been used for centuries to promote hair growth and to prevent HL. This review has explored the efficacy and safety of various HRs, including rosemary, SP, onion juice, KRG, PSO, azelaic acid, olive oil, coconut oil, henna, honey, rice bran extract, Ashwagandha, and amla. This review suggests that these HRs may have potential benefits in promoting hair growth and in treating various forms of HL, such as AGA, TE, and AA. The proposed MOA includes 5α-reductase inhibition, increased microcapillary blood flow, antioxidant, AIP, and modulation of the hair growth signaling pathways. Further research, particularly well-designed, randomized trials with larger sample sizes and longer periods, are needed to confirm these HRs. It is also essential to determine the optimal dosage, formulation, and treatment duration for each HR.

Overall, HRs may offer promising alternative or complementary approach to conventional HL treatment. However, until more robust scientific evidence is available, it is advisable for individuals to consider use of HRs for HL and consult with healthcare professionals to discuss the potential benefits and risks, as well as to ensure appropriate use and safety of these remedies.

Conflict of Interest Statement

The authors declare no conflicts of interest.

Funding Sources

This study received no external funding.

Author Contributions

Dr. Azhar Ahmed conducted the literature search and contributed to writing the manuscript. Dr. Azhar M. Alali contributed to drafting and editing the manuscript. Dr. Ebtesam Abdullah led the organization of the review and contributed to writing and critical revisions. Dr. Mohammed N. Alharbi contributed to writing and provided critical revisions. Dr. Hamza M. Alayoubi assisted in the analysis of findings and final editing of the manuscript. All the authors have read and agreed to the published version of the manuscript.

Funding Statement

This study received no external funding.